sustainability Article Influence of Roof Windows Area Changes on the Classroom Indoor Climate in the Attic Space: A Case Study Erika Dolnikova * , Dusan Katunsky , Marian Vertal and Marek Zozulak Institute of Architectural Engineering, Faculty of Civil Engineering, Technical University of Kosice, 042 00 Kosice, Slovakia; [email protected] (D.K.); [email protected] (M.V.); [email protected] (M.Z.) * Correspondence: [email protected]; Tel.: +421-055-602-4162 Received: 28 April 2020; Accepted: 17 June 2020; Published: 20 June 2020 Abstract: Windows are a complex part of building design and provide a considerable benefit, including to school buildings. For the evaluation of the daylighting conditions prevailing in classrooms, the daylight factor (DF) was considered as the most appropriate parameter for indicating the quantity of admitted daylight. The DF values and CIE overcast sky were calculated using Velux Daylight Visualizer 3 software. The task of the paper is to compare various roof window openings in relation to the level of daylight in the attic, looking to optimize the use of the attic for teaching. The indoor air temperature has a general influence on comfort in the interior, in addition to daylight. In winter, the situation is not critical. The thermal insulation properties of packaging structures are sufficient. The situation is worse in summer, due to the fact that the heat-storage properties are undersized and there is excessive overheating of the indoor air. Four variants of roof windows and their influence on the overall microclimate in the attic are compared. The variant without roof windows is a suitable solution with regard to minimum overheating, but the worst situation for daylight. In order to receive even more light from the window (by moving windows to the top of the roof), we can use variant 2. Based on a combination of daylight calculations and summer temperature, a graphical dependence on window size prediction in terms of top and combined lighting is derived. This was hypothesized without shading the windows. Of course, the shading elements of these windows or cooling are expected in the summer. Finally, the energy required for cooling is compared depending on the size of the windows and achievement of the permissible temperature. Keywords: roof windows; daylighting; attic space; simulation program; school building 1. Introduction Daylight systems should provide a sufficient level of daylight in the classroom for activities, such as reading and writing. The level and quality of daylight in the classroom is important for the health of students, and it also affects their academic performance and participation in the teaching process. Daylight is a critical design factor for those interested in global warming, carbon emissions and sustainable design—in addition to visual comfort. Creating an ideal classroom environment depends on so many different factors (see Figure1), including the structure of the building, classroom size, windows, orientation to the cardinal, glare protection, interior equipment, color of surfaces, etc. [1]. Sustainability 2020, 12, 5046; doi:10.3390/su12125046 www.mdpi.com/journal/sustainability Sustainability 2020, 12, x FOR PEER REVIEW 2 of 24 subjectiveSustainability 2020perception, 12, 5046 of space, and ensures an adequate level of vision with good uniformity2 of of 24 lighting. Its application also saves energy on artificial lighting [2]. Windows and View Productivity and Human Factors Satisfaction in Daylight Design Controlling Daylight in Interior Spaces Minimize Glare Figure 1.1. 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BecauseStudents visual who learn activities during such the as day reading can also and experience writing are health very benefits important such during as improved the educational immunity, phase,growth, it is and essential vision to due create to sucomfortablefficient daylight. visual conditions The appropriate in school design buildings of daylight that will constructions contribute to theseprovides activities. a connection Two elements between of the sustainable indoor and building outdoor environment,design which ahave suitable direct subjective effects on perception student performanceof space, and are ensures natural an adequatedaylighting level and of visionindoor with air quality. good uniformity Recent studies of lighting. on the Its effect application of natural also daylightsaves energy in schools on artificial revealed lighting that, [2 ].besides different health benefits, students perform better in daylightedBecause classrooms visual activities [3,4]. such as reading and writing are very important during the educational phase,The it isamount essential of energy to create consumption comfortable in visual a building conditions mainly in schooldepends buildings on its fenestration that will contribute system. 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Proper daylighting in a school environment is very complex task. The energy consumption of . Better utilization of daylight accompanied with proper management; classroom lighting can reach up to 50% of the school’s total electricity costs—this is because the energy . Regular cleaning of windows and bulbs from dust; this can save energy in light; used for lighting is consumed at a daily rate, and is expensive [9,10]. Adequate and high-quality . Incorrect lamp maintenance can absorb up to 50% of light through a thick layer of dust; lighting is a very important part of our daily activities. When leaving the room, the last obligation is always to turn off the light. Energy saving options without cost include [11,12]: The level of light incidences from above is higher. Lighting and brightness increases from Better utilization of daylight accompanied with proper management; horizon to zenith. Therefore, roof windows provide at least twice as much light as vertical windows of Regularthe same cleaning size, and of three windows times and that bulbs of dormers from dust; of the this same can save size energy(see Figure in light; 2). The roof window provides Incorrect a greater lamp maintenance possibility of can combining absorb up lighting to 50% levels of light [13–15]. through The a thickdaylight layer level of dust; is described by the When daylight leaving factor the (see room, equation the last 5). obligation is always to turn off the light. The minimum and average daylight factors are defined in the standard [16], STN 730580; The level of light incidences from above is higher. Lighting and brightness increases from horizon Daylighting in buildings, Part-1 Basic requirements, and the standard [17] EN 12464-1:2012. Light to zenith. Therefore, roof windows provide at least twice as much light as vertical windows of the and Lighting; Lighting of Work Places-Part 1: Indoor Work Places. Several practical exercises have same size, and three times that of dormers of the same size (see Figure2). The roof window provides been carried out to assess the impact of external outlook on well-being. The standard level was a greater possibility of combining lighting levels [13–15]. The daylight level is described by the daylight assessed through the analysis of many classes [18]. The quality of lighting assessment in university factor (see equation 5). classrooms is the subject of [19]. The uniformity of lighting plays a very important role in regulations, Sustainability 2020, 12, x FOR PEER REVIEW 3 of 24 Sustainabilityand should2020 be, 12clear, 5046